package com.gyh.system.common.utils;

import org.apache.commons.lang3.Validate;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.annotation.Lazy;
import org.springframework.stereotype.Service;

/**
* @author 作者 gyh:
* @version 创建时间：2018年1月6日 下午5:08:43
* 以静态变量保存Spring ApplicationContext, 可在任何代码任何地方任何时候取出ApplicaitonContext.
*/
@Service
@Lazy(false)
public class SpringContextHolder implements ApplicationContextAware , DisposableBean{

	private static Logger logger = LoggerFactory.getLogger(SpringContextHolder.class);
	
	private static ApplicationContext applicationContext = null;

	/**
	 * 获取存储在静态变量中的ApplicationContext
	 * @return
	 */
	public  static ApplicationContext getApplicationContext() {
		assertContextInjected();
		return applicationContext;
	}
	
	/**
	 * 从静态变量applicationContext中取得Bean, 自动转型为所赋值对象的类型.
	 * @param beanName
	 * @return
	 */
	@SuppressWarnings("unchecked")
	public static <T> T getBean(String beanName) {
		assertContextInjected();
		return (T) applicationContext.getBean(beanName);
	}
	
	/**
	 * 从静态变量applicationContext中取得Bean, 自动转型为所赋值对象的类型.
	 */
	public static <T> T getBean(Class<T> requiredType) {
		assertContextInjected();
		return applicationContext.getBean(requiredType);
	}
	
	/**
	 * 清除SpringContextHolder中的ApplicationContext为Null.
	 */
	public static void clearHolder() {
		if (logger.isDebugEnabled()){
			logger.debug("清除SpringContextHolder中的ApplicationContext:" + applicationContext);
		}
		applicationContext = null;
	}
	
	
	@Override
	public void destroy() throws Exception {
		SpringContextHolder.clearHolder();
	}

	/**
	 * 实现ApplicationContextAware接口，注入Context到静态变量中
	 */
	@Override
	public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
		SpringContextHolder.applicationContext = applicationContext;
	}
	
	/**
	 * 检查ApplicationContext不为空.
	 */
	public static void assertContextInjected() {
		Validate.validState(applicationContext != null, "applicaitonContext属性未注入, 请在添加注解和在Xml中进行Bean的注入");
	}

}
